四川农业大学研究生，四川农业大学研究生院
近日，四川农业大学动物医学院陈舜团队国际知名期刊JBC发表题为“TLR4和肠道共生菌LPS协同调控禽黄病毒感染分子机制“的研究论文，本研究首次报道了蚊媒黄病毒的胃肠道感染传播模式并解析其调控机制。
坦布苏病毒病是由坦布苏病毒感染所导致的以蛋鸭产蛋骤降、青年鸭生长迟缓等为主要特征的禽类重要传染病。该病毒可感染几乎所有禽类，对雏鼠有致病力，该病一般经蚊等媒介昆虫叮咬吸血而传播。但是，研究团队对过去10年的流行监控中观察到该病在蚊虫不活跃的深秋和冬季仍频频爆发，由此提示着该病毒可能存在非蚊媒传播的方式，并由此提出坦布苏病毒经消化道传播的设想。
为了解答坦布苏病毒是否可以经胃肠道感染并解析其机制，研究团队首先以口服灌喂病毒或/和特定抗生素而建立坦布苏病毒鸭胃肠道体内感染模型，明确坦布苏病毒可以经胃肠道入侵而建立感染；接着以体外感染模型明确病毒囊膜蛋白E、细菌LPS、TLR4是病毒胃肠道入侵的关键；最后以单轮感染假病毒、基因敲低模型、蛋白互作分析法等解析三者的相互调控机制：TLR4可与坦布苏病毒E蛋白特异性结合而被病毒利用为细胞入侵受体；细菌LPS作为中间体可显著促进病毒E蛋白与TLR4的互作；TMUV E-LPS-TLR4的互作显著抑制了宿主炎性免疫反应的激活，（详见下图）。
图1. TMUV E、LPS、TLR4三者协同互作模式图
A LPS和TLR4协同TMUV的吸附进入。B. TMUV和LPS长时间互作会导致病毒不稳定降解。
该研究得到了自然科学基金、中国-中东欧联合项目、四川省国际科技合作重点项目项目的大力支持。博士研究生吴震为第一作者，程安春教授、陈舜教授为共同通讯作者。
附论文信息：
Title：Toll-like receptor 4 and lipopolysaccharide from commensal microbes regulate Tembusu virus infection
DOI：10.1016/j.jbc.2022.102699
Abstract：Unlike most flaviviruses transmitted by arthropods, Tembusu virus (TMUV) is still active during winter and causes outbreaks in some areas, indicating vector-independent spread of the virus. Gastrointestinal transmission might be one of the possible routes of vector-free transmission, which also means that the virus has to interact with more intestinal bacteria. Here, we found evidence that TMUV indeed can transmit through the digestive tract. Interestingly, using an established TMUV disease model by oral gavage combined with an antibiotic treatment, we revealed that a decrease in intestinal bacteria significantly reduced local TMUV proliferation in the intestine, revealing that the bacterial microbiome is important in TMUV infection. We found that lipopolysaccharide (LPS) present in the outer membrane of Gram-negative bacteria enhanced TMUV proliferation by promoting its attachment. Toll-like receptor 4 (TLR4), a cell surface receptor, can transmit signal from LPS. We confirmed co-localization of TLR4 with TMUV envelope (E) protein as well as their interaction in infected cells. Coherently, TMUV infection of susceptible cells was inhibited by an anti-TLR4 antibody, purified soluble TLR4 protein, and knockdown of TLR4 expression. LPS-enhanced TMUV proliferation could also be blocked by a TLR4 inhibitor. Meanwhile, pre-treatment of duck primary cells with TMUV significantly impaired LPS-induced IL6 production. Collectively, our study provides first insights into vector-free transmission mechanisms of flaviviruses.
四川农业大学研究生(四川农业大学研究生院)
